1. Field of the Invention
The invention relates to a dual gauge track system and a transfer car therefor, and more particularly to such a system wherein the transfer car may travel from a loading position to an unloading position and be turned at least 90.degree. at the unloading position in a minimum of space.
2. Description of the Prior Art
The track arrangement and transfer car therefor of the present invention may have many applications. While not intended to be so limited, for purposes of an exemplary showing the present invention will be described in its application to the transfer of scrap from a steel mill scrap yard building to the charging floor of a building containing one or more scrap melting furnaces such as, for example, basic oxygen furnaces. In the usual steel mill layout, a track scale constitutes the starting point of the transfer car in the scrap yard building. The transfer car supports a large scrap box provided on its sides with trunnions. Once the scrap box is loaded with a desired amount of scrap the transfer car is conducted to the charging floor of the basic oxygen furnace building which is generally in line with the scrap yard building. In order for the hooks of an overhead crane in the basic oxygen furnace building to engage the trunions of the scrap box to lift and shift the scrap box to its ultimate charging position, the transfer car and the scrap box mounted thereon must be turned 90.degree. within the building. The charging floor affords minimum room to accomplish this turning of the transfer car.
The present practice is to rotate the transfer car on the charging floor by the use of a railroad-type turn table. The turn table is recessed in a concrete pit in the charging floor and is rotated on a circular rail by motor and gear reducer means. This means of rotating the transfer car is characterized by a number of deficiencies. First of all, the installation costs are high. In addition, maintance costs are also high and track alignment and control problems ae inherent in the system.
Another approach to the problem of the turning of a transfer car is illustrated in U.S. Pat. No. 3,139,839. This approach utilizes a single track system with a branching spur. The track system requires special rail without benefit of frogs, some of which presents a broad flat top and some of which is longitudinally grooved. On the transfer car itself, swiveltype trucks are provided, selected wheels of which are unflanged and the remaining wheels of which are provided with a central flange to engage that portion of the rail structure which is grooved. This arrangement assures that as the transfer car reaches the spur the lead truck will follow the spur and the following truck will continue with its direction of travel unchanged. This approach is also characterized by certain deficiencies. First of all it requires special track which in turn requires special patterns and is expensive and difficult to install. Excessive wear will occur on soft cast steel flat rail causing frequent rail replacement and shut-down time, both of which add to the expense. Since special track is required, the system cannot be tied into the regular railroad track system of a steel mill. The lead truck makes a full 90.degree. turn to turn the transfer car and the spur therefor has a length of curve sufficient to enable this full 90.degree. turn. As a result a short radius curve is required. This would not lend itself to the use of standard railroad rail, first of all because it is not a dual-track system, and secondly, because such a short radius curve would result in excessive friction between a standard flanged railroad-type wheel and the rail. Furthermore, the standard practice of reducing friction on short radius curves by spreading the gage could not be practiced in a situation utilizing a center flanged wheel and a grooved rail.
The system taught in the above mentioned patent would require the special rail to be cast in relatively short sections rather than using standard lengths of standard railroad-type rail. Difficulties would be encountered in providing a cast rail with a groove in the center of sufficient strength to support the wheel loadings contemplated with the steel mill scrap transfer car of the present invention. Assuming an 8 wheeled transfer car, wheel loadings in excess of 36,000 pounds might well be experienced. Such wheel loadings would soon roll the special grooved rail flat, destroying its shape. Wheel loadings of this magnitude would also severly damage center flanged wheels of the type required by the patent. Finally, the accumulation of fine scrap in the groove of a grooved rail could cause a wedging of the center flanged wheels or a derailment.
The present invention provides a track system and transfer car therefor which obviates the above enumerated deficiencies. The system of the present invention requires only track maintance, having no alignment problems. Since standard rail and standard flanged wheels are used, installation costs are far less and maintance is considerably easier. The arrangement of the present invention has low power requirements and can be operated by a very simple control system.
In accordance with the system of the present invention, the outwardly turned lead truck rails are so configured that it is not necessary for the lead truck to turn 90.degree. to achieve a 90.degree. turn of the transfer car. This permits a larger radius for the curved portion of the lead truck rail set and enables the curved portion to be shorter. As a consequence of this, the lead truck of the transfer car will negotiate the turn with ease and friction between its wheels and the rails will be reduced. Far less space is required enabling two transfer systems of the present invention to be utilized on the same charging floor in a minimum space and without crossing each other. With minor modifications, the track system to be described may be used to turn the transfer car 180.degree. or even 360.degree..
The track system of the present invention can be tied into or can be an integral part of the regular railroad track system of a steel mill, depending upon the track gauge selected. Furthermore, the transfer car of the present invention demonstrates markedly improved stability.